“Renovation wave” – a chance for autoclaved aerated concrete

In partnership with AAC worldwide we will show in several articles over the following months how the policy initiatives proposed by the Commission in its Communication on the Green Deal can be realised with the help of AAC in times of increasing urbanisation and need for affordable housing. To begin with, we will showcase how AAC can be efficiently and intelligently used in renovation processes. Within the Green Deal, the Commission promised to put forward an initiative for a so-called “Renovation wave” in Summer 2020, aiming to set incentives that shall lead to a doubling or even tripling of the annual renovation rate across Europe.

This initiative is urgently needed considering the current low rate (around 1.3%) and the amount of old post-war building stock that is unfit in terms of energy-efficiency, air quality and security levels.

The renovation process of the famous “Europa building”

A very recent case of AAC usage in renovation processes – at the very heart of Europe - is one of the most extraordinary and impressive buildings in Brussels: the “Europa building”. After the European Union’s expansion in 2004, the Council of the EU as well as the European Council had to find a new and larger meeting location for their headquarters in Brussels. Ministerial meetings and quarterly summits of the heads of State of the EU member countries used to be held in the Justus Lipsius building, which did not meet their needs anymore. The decision was made to integrate parts of the “Résidence Palace”, a historic but outdated building into the neighbouring Justus Lipsius complex.

The task however was a difficult one, as the build- ing parts that were to be connected needed to be renovated and expanded to fit the high requirements of European decision-makers, while simultaneously complying with new regulations in the field of energy consumption and air quality. To add to the complexity, the historic Art déco façades of the Résidence Palace were protected and had to be preserved. Originally constructed between 1922 and 1927, the building used to be a luxury apartment building for the rich Brussels bourgeoisie, including a hotel, swimming pool and theatre, as well as tennis courts on the roof. After 1945, the complex became an office building for the Belgian government.

The delicate project found its perfect candidate: the Belgian architect Philippe Samyn with his company Samyn & Partners. An architect who during his career has always looked for challenging projects and uses his knowledge as an engineer to produce buildings as lean and efficiently as possible. Over 12 years, Samyn and his team carefully designed the building, resulting in 13,000 drawings, and two comprehensive and detailed books that Samyn released in 2013 and 2016.

The goal was to make this place explicit, symbolic beyond purely functional, as well as visible from the public space, even in the evening through well- placed lighting. All floors of the building are designed in an elliptical shape, showing differences in dimension but having the same center. The visual result is an opal-shaped “lantern” mounted with glass panels that maintain daylight in all corridors, rooms and halls, creating a symmetrical structure with a high atrium inside an outer double-walled glas façade. The building provides a large amount of conference rooms surrounded by a daylight circulation zone as well as comfortable cafeterias, restaurants and dining halls. By centrally positioning the lantern surrounded by offices in the carefully renovated Résidence Palace, Samyn achieved a split between pragmatic and serving functions as well as modern design.

Samyn showed his architectural and engineering skills not only in the construction of the façade, where he chose to use thirty percent less steel than firstly planned. He also had to overcome problems such as limited foundation possibilities due to the underground railway that bordered the building, high security requirements for the top-level diplomatic meetings, the modernization of the historic complex without changing the outer façades, energy performance improvement and an enlargement with additional walls and floors. Luckily, Samyn had con- tacts to AAC producer Xella from Germany, one of the largest members of EAACA. He first discovered Xella products at a construction exhibition in Munich and was keen on using the material to solve some of his problems with the Résidence Palace. AAC was again able to prove its strength as a complementary building material for difficult and large renovation processes.

AAC as the key ingredient for the complex renovation of a high-security heritage

AAC products that was especially useful during the renovation were the mineral insulation boards of the Xella brand “multipor”, which were used for the thermal insulation of existing facades.

The multipor products were in this case especially important as they were used inside insulation through a “vapor-open insulation” approach, which was crucial for such a heritage building. An exterior insulation was not an option because the historic outer façade had to remain intact. Next to the strong thermal insulation capability that met high energy efficiency requirements, additional benefits of multipor products in the renovation process were their lightweight, easy handling and a high fire protection features.

Furthermore, the Xella product was vital in delivering a healthy indoor air quality level throughout the building, as well as for meeting the environmental requirements and European Technical Assessment (ETA) standards of the EU buildings through their sustainable production processes.

Finally, Samyn’s use of Building Information Modelling (BIM) technology proved to be decisive for the renovation and building process. The most innovative software was further used for the calculation of humidity transmission and temperature risk assessments to evaluate and lower the possibility of condensation and accumulation of moisture in the interior insulation.

This project for the European Council showed impressively how AAC was essential to achieve the most stringent standards for an energy-efficient, environ- mentally-friendly, modern and highly representative building. Samyn managed to renovate and integrate an outdated building and turn it into a highly functional, as well as symbolic, piece of art in the heart of Europe, while preserving its historical design - by using his skills as an engineer and the unique features of the multi-deployable material AAC.

The renovation of the Residence Palace for the Council’s new “Europa building” is not the only famous renovation project in Brussels that featured an ex- tensive use of AAC products. Other examples are the “Berlaymont” of the European Commission or the “Palatium”. Next time you walk past these buildings, you might look at them with different eyes.

EAACA – European Autoclaved Aerated Concrete Association
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